Joy and Jacques go over the Optics section of the systematics listed here

IP is separated in two effects: sky T→P leakage from sky T converted to sky P through IP, and polarization load/noise coming from instrument emitted T converted to P through IP (ex: mirror T emissions converted to P through lens IP).

Many optic effects are hard to assess without a more detailed knowledge of the optical chain

Overall, Jacques thinks the optical beam systematic effects will be very important and need to be simulated and studied in details.

Note that end-to-end beam calibration on the ground will not be possible as the instrument cannot be cooled on the ground.

For pointing, given the probe's beam size, effects should be similar to what was studied for Core.